Mobile wireless communications device with separate in-phase (i) and quadrature (q) phase power amplification and power amplifier pre-distortion and iq balance compensation

ABSTRACT

A communications device, in one aspect as a portable wireless communications device, includes an in-phase modulator and power amplifier that receives a baseband I signal and modulates and amplifies the I signal. A quadrature modulator and power amplifier receives a baseband Q signal and modulates and amplifies the Q signal. A power combiner sums and outputs the I and Q signals. An I demodulator circuit receives a signal fed back from the I power amplifier and demodulates the fed back signal to produce demodulated I signals. A Q demodulator circuit receives a signal fed back from the Q power amplifier and demodulates the fed back signal to produce demodulated Q signals. A processor compares the digital, baseband I and Q signals with a demodulated I and Q signals to compensate for amplitude, frequency and phase modulation errors.

TECHNICAL FIELD

The present disclosure relates to the field of communications devices,and more particularly, to mobile wireless communications devices andrelated methods.

BACKGROUND

Mobile wireless communications device have advanced radio frequency (RF)processing circuits and receive or transmit radio communications signalstypically using modulation schemes with In-phase (I) and Quadrature (Q)modulation and demodulation circuits that sometimes create linearityissues with power amplifiers and sometimes suffer poor antenna match.This can cause some degradation of TRP (total radiated power) and raiseharmonic interference issues because of the higher non-linearity of apower amplifier, as an example.

Commonly assigned and copending patent application Ser. No. 12/173,045filed Jul. 15, 2008, the disclosure which is hereby incorporated byreference in its entirety, addresses some of these issues and uses amobile wireless communications device having a housing and antennamounted within the housing. Radio frequency (RF) circuitry is carriedwithin the housing, such as typically on at least one circuit board. Itincludes a transceiver connected to the antenna through which RFcommunication signals are transmitted and received. A processor isoperative with the RF circuitry. A transceiver includes an In-phase andQuadrature (I/Q) Modulation and Power Amplification circuit and includesan In-phase (I) circuit having an In-phase signal input and a modulatormixer and power amplifier circuit that receives the In-phase signal andamplifies the In-phase signal. A Quadrature (Q) circuit includes aQuadrature signal input and a modulator mixer and power amplifiercircuit that receives the Quadrature signal and amplifies the Quadraturesignal. A power combiner receives the separately amplified In-phase andQuadrature signals and sums and outputs the signals as a combined I andQ signal.

This type of circuit described in the incorporated by reference '045application provides an IQ modulation and power amplification circuitwith respective power amplifier circuits in each of the I and Qcircuits. It allows greater control over any power amplifier driverand/or power amplifier biasing, even when using either open loop systemsor the larger or smaller closed loop systems. It is possible for thequadrature hybrid power combiner to be tolerable to the mismatch ofantenna load impedance and give greater reflectivity for phase andfrequency modulation, allowing efficient amplitude modulation to occurby changing the bias of the power amplifier circuits for each of the Iand Q circuits and give greater flexibility and circuit function.

It has been found that greater improvements in this circuit aredesirable concerning linearity with respect to I and/or Q poweramplifiers and I and Q amplitude and phase imbalance issues. It wouldalso be advantageous to address efficiency issues of the I and Q poweramplifiers when using a different radio frequency (RF) output powerlevel.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages will become apparent from thedetailed description which follows, when considered in light of theaccompanying drawings in which:

FIG. 1 is a schematic block diagram of an example of a mobile wirelesscommunications device configured as a handheld device and illustratingbasic internal components thereof as a non-limiting example.

FIG. 2 is a front elevation view of the mobile wireless communicationsdevice of FIG. 1.

FIG. 3 is a schematic block diagram showing basic functional circuitcomponents that can be used in the mobile wireless communications deviceof FIGS. 1-2.

FIG. 4 is a block diagram of a conventional In-phase and Quadrature(I/Q) modulation and power amplification circuit showing one poweramplification circuit after combining I/Q signals.

FIG. 5 is a block diagram of an In-phase and Quadrature modulation andpower amplification circuit that includes a separate power amplifiercircuit for each of the In-phase and Quadrature circuits in accordancethe type of circuit described in the incorporated by reference andcommonly assigned '045 patent application addressed above.

FIG. 6 is a block diagram showing a portion of an improved In-phase andQuadrature modulation and power amplification circuit compared to thatof FIG. 5 and showing the resulting mathematical calculations associatedwith the functional components and showing the improvement whencombining signals after the quadrature combiner, as illustrated.

FIGS. 7A and 7B are block diagrams of an In-phase and Quadraturemodulation and power amplification circuit in accordance with anon-limiting example and showing the complete functional circuit withfeedback and feed forward to ensure IQ balance compensation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present description is made with reference to the accompanyingdrawings, in which preferred embodiments are shown. However, manydifferent embodiments may be used, and thus the description should notbe construed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete. Like numbers refer to like elements throughout.

A communications device includes an In-phase (I) circuit having anin-phase modulator and mixer circuit and I power amplifier circuit thatreceives a digital, baseband I signal and modulates and amplifies the Isignal. A Quadrature (Q) circuit includes a quadrature modulator andmixer circuit and a Q power amplifier circuit that receives a digital,baseband Q signal and modulates and amplifies the Q signal. A powercombiner receives the separately amplified I and Q signals and sums andoutputs the I and Q signals as a combined I and Q signal. An Idemodulator circuit receives a signal fed back from the I poweramplifier and demodulates the fed back signal to produce demodulated Isignals. A Q demodulator circuit receives a signal fed back from the Qpower amplifier and demodulates the fed back signal to producedemodulated Q signals. A processor compares the digital, baseband I andQ signals with a demodulated I and Q signals to compensate foramplitude, frequency and phase modulation errors wherein I and Q signalinputs are isolated from the combined I and Q signal to enhance antennamatching and transmit radiated power (TRP) and reduce harmonic emissionfrom the respective I and Q power amplifier circuits.

In one aspect, the processor predistorts the digital I and Q signals fedto the I and Q circuits to aid in compensating for the amplitude,frequency and phase modulation errors. The respective in-phase modulatorand mixer circuit can receive and I_Q input signals to produce an Isignal to the I power amplifier and the quadrature modulator and mixercircuit receives Q_I and Q_Q input signals to produce a Q signal to theQ power amplifier. The in-phase modulator and mixer circuit can beformed as a respective I_I mixer and I_Q mixer that receives respectiveI_I and I_Q signals and a frequency divider circuit associated with themixer and I_Q mixer for imparting a 90 degree phase shift and an Isummer for receiving signals from the mixers and producing an I signal.The quadrature modulator and mixer circuit can be formed as a respectiveQ_I mixer and Q_Q mixer that receives respective Q_I and Q_Q signals anda frequency divider circuit associated with the Q_I mixer and Q_Q mixerfor imparting a 90 degree phase shift and a Q summer for receivingsignals from the mixers and producing a Q signal.

The processor can output control signals for controlling each of thepower amplifier circuit and control respective biasing in each poweramplifier circuit and adjust amplitude of a respective I or Q signal. Inanother aspect, each of the I and Q demodulator circuits can be formedas mixers and a frequency divider associated therewith for imparting a90 degree phase shift.

In another aspect, an I/Q demodulator circuit can be connected to theprocessor and receives a signal from the output of the power combiner toaid in determining amplitude, frequency and phase modulation errors. Apower detector can be connected to the processor and receives a signalfrom the output of the power combiner and outputs a signal that iscompared with an original power for compensating for amplitude error.The power combiner can be formed as a 3 dB power combiner. The powercombiner can also be formed as a quadrature hybrid power combiner.

In another aspect, a mobile wireless communications device can includethe circuits as described and be formed as a housing with an antennacarried by the housing and at least one circuit board carried by thehousing. Radio frequency (RF) circuitry can be carried by at least onecircuit board and be formed as a transceiver connected to the antennathrough which the RF communications signals are transmitted andreceived. A processor is carried by the at least one circuit board andoperative with the RF circuitry. This processor can be the sameprocessor that compares the digital, baseband I and Q signals with thedemodulated I and Q signals to compensate for amplitude, frequency andphase modulation errors.

A method aspect is also set forth.

A brief description will now proceed relative to FIGS. 1-3, whichdiscloses an example of a mobile wireless communications device, forexample, a handheld portable cellular radio, which can incorporatenon-limiting examples of the various circuits, including the improvedIn-phase and Quadrature modulation and power amplification circuit aslater described. FIGS. 1-3 are representative non-limiting examples ofthe many different types of functional circuit components and theirinterconnection, and operative for use in the circuits of the mobilewireless communications device that can incorporate the improvements,advantages and features as described.

Referring initially to FIGS. 1 and 2, an example of a mobile wirelesscommunications device 20, such as a handheld portable cellular radiowith improvements and advantages as described below is set forth. Thisdevice 20 illustratively includes a housing 21 having an upper portion46 and a lower portion 47, and at least one dielectric substrate (i.e.,circuit board) 67, such as a conventional printed circuit board (PCB)substrate, for example, carried by the housing. A number of differentcircuit boards can be used for supporting different components. Forexample, one circuit board could support the microprocessor and RFcomponents, another circuit board could be formed as an antenna circuitboard, and yet another circuit board could be formed as a circuit boardfor supporting different components such as a keyboard. Themicroprocessor could be positioned on another circuit board as comparedto other RF components.

A housing (not shown in detail) would typically cover and enclosevarious components, such as one or more circuit boards and one or moreantennae. The housing includes a housing case, for example, a plasticcase. The housing case could support a separate housing cover for frontand rear sides depending on the type of design. Any type of housing orhousing case will allow access to any circuit board and supports the oneor more circuit boards and one or more antennae. A battery openingprovides access for a battery to power the device. The housing casecould support one or more antennae in one non-limiting example, such asat its lower edge. The term circuit board 67 as used hereinafter canrefer to any dielectric substrate, PCB, ceramic substrate or othercircuit carrying structure for carrying signal circuits and electroniccomponents within the mobile wireless communications device 20. Theillustrated housing 21 is a static housing, for example, but it shouldbe understood that a flip or sliding housing can be used as is typicalin many cellular and similar telephones. These and other housingconfigurations with different housing case designs may be used.

Circuitry 48 is carried by the circuit board 67, such as amicroprocessor, memory, one or more wireless transceivers (e.g.,cellular, WLAN, etc.), which includes RF circuitry, including audio andpower circuitry, and in this aspect, including any keyboard circuitry.This circuitry could also generally be termed RF circuitry. It should beunderstood that, as noted before, keyboard circuitry could be on aseparate keyboard, etc., as will be appreciated by those skilled in theart. The different components as described can also be distributed onone circuit board or among a plurality of different circuit boards asnoted before. A battery (not shown) is also preferably carried by thehousing 21 for supplying power to the circuitry 48. The term RFcircuitry could encompass the interoperable RF transceiver circuitry,including receive and transmit circuits and power circuitry, includingcharging circuitry and audio circuitry, including In-phase andQuadrature circuits that include respective power amplifier circuits forrespective In-phase and Quadrature circuits.

In one aspect, an audio output transducer 49 (e.g., a speaker) iscarried by an upper portion 46 of the housing 21 and connected to thecircuitry 48. One or more user input interface devices, such as a keypad(keyboard) 23 (FIG. 2), is also preferably carried by the housing 21 andconnected to the RF circuitry 48. The term keypad as used herein alsorefers to the term keyboard, indicating the user input devices havinglettered and/or numbered keys commonly known and other embodiments,including multi-top or predictive entry modes. Other examples of userinput interface devices include a scroll wheel 37 and a back button 36.Of course, it will be appreciated that other user input interfacedevices (e.g., a stylus or touch screen interface) may be used in otherembodiments.

An antenna and associated antenna circuit 45 (FIG. 1) is preferablysupported within the housing and in one aspect at a lower portion 47 inthe housing, such as on the housing case lower edge. The antenna can beformed as a pattern of conductive traces that make an antenna circuit,which physically forms the antenna. It is operatively connected to thecircuitry 48 on the main circuit board 67 or other circuitry on otherboards. In one non-limiting example, the antenna could be formed on aseparate antenna circuit board or an antenna circuit board section thatextends from the main circuit board at the lower portion of the housing.Also, a separate keyboard circuit board could be used as noted before.Other circuit boards can be used for other components.

More particularly, a user will typically hold the upper portion of thehousing 21 very close to their head so that the audio output transducer49 is directly next to the ear. Yet, the lower portion 47 of the housing21 where an audio input transducer (i.e., microphone) is located neednot be placed directly next to a user's mouth, and can be held away fromthe user's mouth. That is, holding the audio input transducer close tothe user's mouth may not only be uncomfortable for the user, but it mayalso distort the user's voice in some circumstances.

In some designs, the antenna 45 is placed adjacent the lower portion 47of the housing 21 to allow for less impact on antenna performance due toblockage by a user's hand. Users typically hold cellular phones towardsthe middle to upper portion of the phone housing, and are therefore morelikely to put their hands over such an antenna than they are an antennamounted adjacent the lower portion 47 of the housing 21. Accordingly,more reliable performance may be achieved from placing the antenna 45adjacent the lower portion 47 of the housing 21.

Another benefit of this type of configuration is that it provides moreroom for one or more auxiliary input/output (I/O) devices 50 to becarried at the upper portion 46 of the housing. Furthermore, byseparating the antenna 45 from the auxiliary I/O device(s) 50, this mayallow for reduced interference therebetween.

Some examples of auxiliary I/O devices 50 include a WLAN (e.g.,Bluetooth, IEEE 802.11) antenna for providing WLAN communicationcapabilities, and/or a satellite positioning system (e.g., GPS, Galileo,etc.) antenna for providing position location capabilities, as will beappreciated by those skilled in the art. Other examples of auxiliary I/Odevices 50 include a second audio output transducer (e.g., a speaker forspeaker phone operation), and a camera lens for providing digital cameracapabilities, an electrical device connector (e.g., USB, headphone,secure digital (SD) or memory card, etc.).

It should be noted that the term “input/output” as used herein for theauxiliary I/O device(s) 50 means that such devices may have input and/oroutput capabilities, and they need not provide both in all embodiments.That is, devices such as camera lenses may only receive an opticalinput, for example, while a headphone jack may only provide an audiooutput.

The device 20 further illustratively includes a display 22, for example,a liquid crystal display (LCD) carried by the housing 21 and connectedto the circuitry 48. A back button 36 and scroll wheel 37 can also beconnected to the circuitry 48 for allowing a user to navigate menus,text, etc., as will be appreciated by those skilled in the art. Thescroll wheel 37 may also be referred to as a “thumb wheel” or a “trackwheel” in some instances. The keypad 23 illustratively includes aplurality of multi-symbol keys 24 each having indicia of a plurality ofrespective symbols thereon. The keypad 23 also illustratively includesan alternate function key 25, a next key 26, a space key 27, a shift key28, a return (or enter) key 29, and a backspace/delete key 30.

The next key 26 is also used to enter a “*” symbol upon first pressingor actuating the alternate function key 25. Similarly, the space key 27,shift key 28 and backspace key 30 are used to enter a “0” and “#”,respectively, upon first actuating the alternate function key 25. Thekeypad 23 further illustratively includes a send key 31, an end key 32,and a convenience (i.e., menu) key 39 for use in placing cellulartelephone calls, as will be appreciated by those skilled in the art.

Moreover, the symbols on each key 24 are arranged in top and bottomrows. The symbols in the bottom rows are entered when a user presses akey 24 without first pressing the alternate function key 25, while thetop row symbols are entered by first pressing the alternate functionkey. As seen in FIG. 2, the multi-symbol keys 24 are arranged in thefirst three rows on the keypad 23 below the send and end keys 31, 32.Furthermore, the letter symbols on each of the keys 24 are arranged todefine a QWERTY layout. The letters on the keypad 23 are presented in athree-row format, with the letters of each row being in the same orderand relative position as in a standard QWERTY keypad.

Each row of keys (including the fourth row of function keys 25-29) isarranged in five columns in this non-limiting example. The multi-symbolkeys 24 in the second, third, and fourth columns of the first, second,and third rows have numeric indicia thereon (i.e., 1 through 9)accessible by first actuating the alternate function key 25. Coupledwith the next, space, and shift keys 26, 27, 28, which respectivelyenter a “*”, “0”, and “#” upon first actuating the alternate functionkey 25, as noted above, this set of keys defines a standard telephonekeypad layout, as would be found on a traditional touch-tone telephone,as will be appreciated by those skilled in the art.

Accordingly, the mobile wireless communications device 20 as describedmay advantageously be used not only as a traditional cellular phone, butit may also be conveniently used for sending and/or receiving data overa cellular or other network, such as Internet and email data, forexample. Of course, other keypad configurations may also be used inother embodiments. Multi-tap or predictive entry modes may be used fortyping e-mails, etc. as will be appreciated by those skilled in the art.

In one non-limiting aspect, the antenna 45 is preferably formed as amulti-frequency band antenna, which provides enhanced transmission andreception characteristics over multiple operating frequencies. Moreparticularly, the antenna 45 is designed to provide high gain, desiredimpedance matching, and meet applicable SAR requirements over arelatively wide bandwidth and multiple cellular frequency bands. By wayof example, in one non-limiting example, the antenna 45 preferablyoperates over five bands, namely a 850 MHz Global System for MobileCommunications (GSM) band, a 900 MHz GSM band, a DCS band, a PCS band,and a WCDMA band (i.e., up to about 2100 MHz), although it may be usedfor other bands/frequencies as well. To conserve space, the antenna 45may advantageously be implemented in three dimensions although it may beimplemented in two-dimensional or planar embodiments as well. In onenon-limiting example, it is L-configured and positioned at the lowerportion or edge of the support case.

The mobile wireless communications device shown in FIGS. 1 and 2 canincorporate email and messaging accounts and provide different functionssuch as composing e-mail, PIN messages, and SMS messages. The device canmanage messages through an appropriate menu that can be retrieved bychoosing a messages icon. An address book function could add contacts,allow management of an address book, set address book options and manageSIM card phone books. A phone menu could allow for the making andanswering of phone calls using different phone features, managing phonecall logs, setting phone options, and viewing phone information. Abrowser application could permit the browsing of web pages, configuringa browser, adding bookmarks, and changing browser options. Otherapplications could include a task, memo pad, calculator, alarm andgames, as well as handheld options with various references.

A calendar icon can be chosen for entering a calendar program that canbe used for establishing and managing events such as meetings orappointments. The calendar program could be any type of messaging orappointment/meeting program that allows an organizer to establish anevent, for example, an appointment or meeting.

A non-limiting example of various functional components that can be usedin the exemplary mobile wireless communications device 20 of FIGS. 1 and2 is further described in the example below with reference to FIG. 3.The device 20 illustratively includes a housing 120 shown in outline bythe dashed lines, a keypad 140, and an output device 160. The outputdevice 160 shown is preferably a display, which is preferably a fullgraphic LCD. Other types of output devices may alternatively be used. Aprocessing device 180 such as a microprocessor is contained within thehousing 120 and is coupled between the keypad 140 and the display 160.The processing device 180 controls the operation of the display 160, aswell as the overall operation of the mobile device 20, in response toactuation of keys on the keypad 140 by the user.

The housing 120 may be elongated vertically, or may take on other sizesand shapes (including clamshell housing structures). The keypad mayinclude a mode selection key, or other hardware or software forswitching between text entry and telephony entry.

In addition to the processing device 180, other parts of the mobiledevice 20 are shown schematically in FIG. 3. These include acommunications subsystem 101; a short-range communications subsystem102; the keypad 140 and the display 160, along with other input/outputdevices 106, 108, 110 and 112; as well as memory devices 116, 118 andvarious other device subsystems 121. The mobile device 20 is preferablya two-way RF communications device having voice and data communicationscapabilities. In addition, the mobile device 20 preferably has thecapability to communicate with other computer systems via the Internet.

Operating system software executed by the processing device 180 ispreferably stored in a persistent store, such as the flash memory 116,but may be stored in other types of memory devices, such as a read onlymemory (ROM) or similar storage element. In addition, system software,specific device applications, or parts thereof, may be temporarilyloaded into a volatile store, such as the random access memory (RAM)118. Communications signals received by the mobile device may also bestored in the RAM 118.

The processing device 180, in addition to. its operating systemfunctions, enables execution of software applications 130A-130N on thedevice 20. A predetermined set of applications that control basicdevice-operations, such as data and voice communications 130A and 130B,may be installed on the device 20 during manufacture. In addition, apersonal information manager (PIM) application may be installed duringmanufacture. The PIM is preferably capable of organizing and managingdata items, such as e-mail, calendar events, voice mails, appointments,and task items. The PIM application is also preferably capable ofsending and receiving data items via a wireless network 141. Preferably,the PIM data items are seamlessly integrated, synchronized and updatedvia the wireless network 141 with the device user's corresponding dataitems stored or associated with a host computer system.

Communication functions, including data and voice communications, areperformed through the communications subsystem 101, and possibly throughthe short-range communications subsystem. The communications subsystem101 includes a receiver 150, a transmitter 152, and one or more antennae154 and 156. In addition, the communications subsystem 101 also includesa processing module, such as a digital signal processor (DSP) 158, andlocal oscillators (LOs) 161. The specific design and implementation ofthe communications subsystem 101 is dependent upon the communicationsnetwork in which the mobile device 20 is intended to operate. Forexample, the mobile device 20 may include a communications subsystem 101designed to operate with the Mobitex™, Data TAC™ or General Packet RadioService (GPRS) mobile data communications networks, and also designed tooperate with any of a variety of voice communications networks, such asAMPS, TDMA, CDMA, PCS, GSM, etc. Other types of data and voice networks,both separate and integrated, may also be utilized with the mobiledevice 20.

Network access requirements vary depending upon the type ofcommunication system. For example, in the Mobitex and DataTAC networks,mobile devices are registered on the network using a unique personalidentification number or PIN associated with each device. In GPRSnetworks, however, network access is associated with a subscriber oruser of a device. A GPRS device therefore requires a subscriber identitymodule, commonly referred to as a SIM card, in order to operate on aGPRS network.

When required network registration or activation procedures have beencompleted, the mobile device 20 may send and receive communicationssignals over the communication network 141. Signals received from thecommunications network 141 by the antenna 154 are routed to the receiver150, which provides for signal amplification, frequency down conversion,filtering, channel selection, etc., and may also provide analog todigital conversion. Analog-to-digital conversion of the received signalallows the DSP 158 to perform more complex communications functions,such as demodulation and decoding. In a similar manner, signals to betransmitted to the network 141 are processed (e.g., modulated andencoded) by the DSP 158 and are then provided to the transmitter 152 fordigital to analog conversion, frequency up conversion, filtering,amplification and transmission to the communication network 141 (ornetworks) via the antenna 156.

In addition to processing communications signals, the DSP 158 providesfor control of the receiver 150 and the transmitter 152. For example,gains applied to communications signals in the receiver 150 andtransmitter 152 may be adaptively controlled through automatic gaincontrol algorithms implemented in the DSP 158.

In a data communications mode, a received signal, such as a text messageor web page download, is processed by the communications subsystem 101and is input to the processing device 180. The received signal is thenfurther processed by the processing device 180 for an output to thedisplay 160, or alternatively to some other auxiliary I/O device 106. Adevice user may also compose data items, such as e-mail messages, usingthe keypad 140 and/or some other auxiliary I/O device 106, such as atouchpad, a rocker switch, a thumb-wheel, or some other type of inputdevice. The composed data items may then be transmitted over thecommunications network 141 via the communications subsystem 101.

In a voice communications mode, overall operation of the device issubstantially similar to the data communications mode, except thatreceived signals are output to a speaker 110, and signals fortransmission are generated by a microphone 112. Alternative voice oraudio I/O subsystems, such as a voice message recording subsystem, mayalso be implemented on the device 20. In addition, the display 160 mayalso be utilized in voice communications mode, for example to displaythe identity of a calling party, the duration of a voice call, or othervoice call related information.

Any short-range communications subsystem enables communication betweenthe mobile device 20 and other proximate systems or devices, which neednot necessarily be similar devices. For example, the short-rangecommunications subsystem may include an infrared device and associatedcircuits and components, or a Bluetooth™ communications module toprovide for communication with similarly-enabled systems and devices.

Referring now to FIG. 4, there is illustrated a block diagram of aconventional In-phase and Quadrature (I/Q) modulation and poweramplification circuit illustrated generally at 300 that is typicallyused in many different types of communications devices, especially lowerpower mobile wireless communications devices. The circuit 300 has onepower amplifier circuit after the In-phase and Quadrature modulation andmixing and power combining.

FIG. 4 shows this conventional I/Q modulation and power amplificationcircuit 300. It has In-phase and Quadrature inputs (I) and (Q) for arespective In-phase circuit 302 and Quadrature circuit 304 that eachinclude a respective digital-to-analog converter (DAC) 310, 312, lowpass filter 314, 316 and mixer 318, 320 as illustrated. A localoscillator 330 generates a local oscillator (LO) signal into a frequencydivider 332, which passes the resulting and divided signals into therespective mixers 318, 320 as illustrated. The frequency divider 332provides for +45 and −45 phase/frequency adjustment for I and Qmodulation.

The output from the mixers 318, 320 are combined (or summed) at a powercombiner 340 into one signal that is then bandpass filtered within arespective bandpass filter 342. One or more RF power amplifiers form apower amplifier circuit 350 amplifies the signal after bandpassfiltering. The amplified signal is then filtered in a low pass filter352. The filtered signal is passed to further RF circuits for otherprocessing, including an antenna as part of any transmitter circuitryfor signal transmission over-the-air. The modulation and poweramplification circuit 300 shown in FIG. 4 may have linearity issues withthe power amplifier (PA) circuit 350 and requires a more flexible IQmodulation scheme. This can be especially relevant when the poweramplifier circuit design is used for 8 PSK (phase shift keying),quadrature amplitude modulation (QAM) and similar modulation schemes,typical in some lower power communications devices.

This conventional circuit 300 also may have a poor antenna matchdegrading total radiated power (TRP) and cause less efficiency becauseof the current power amplifier drawbacks, making it difficult to makeimprovements in radio frequency transmitter performance and batterylife. Also, this type of conventional circuit 300 may have harmonicsissues because of the higher non-linearity of the power amplifier. Somevery high power I/Q modulation circuits such as in large and powerfulbase stations may use multiple power amplifiers that are power combinedinto an antenna, but they typically incorporate complex circuit featuressuch as feed forward, feedback, free-distortion, complex mixing andcomplex power amplifier circuits. Those types of solutions are notalways adequate for lower power mobile wireless communications device.Some communications circuits for I/Q modulation incorporate paralleloutput stages. These are usually targeted to achieve better linearity inany power amplifier circuit. The parallel output stages are sometimesused for heat control, increased power output, signal quality, peakpower improvement and similar aspects. These circuits still may sufferdrawbacks and may not be as reliable or adapted for lower powerapplication as indicated above.

FIG. 5 is a block diagram of an IQ modulation and power amplificationcircuit 400 such as described in the commonly assigned and copending'045 application identified above that includes I/Q signal inputs and anIn-phase circuit 402 and Quadrature circuit 404, including the basiccomponents in each I/Q circuit 402, 404 of a respective DAC 410, 412,LPF 414, 416 and mixer 418, 420. These components are similar tocomponents shown in FIG. 4, but with modifications that could be made asa result of the changes in each I/Q circuit 402, 404 to include a poweramplifier circuit as described below. FIGS. 6, 7A and 7B describeimprovements to the circuit described relative to FIG. 5, and thedescription of that circuit shown in FIGS. 6, 7A and 7B will proceedafter describing the circuit in FIG. 5.

As shown in FIG. 5, each I/Q circuit 402, 404 includes a power amplifiercircuit 450 a, 450 b that is used only for amplifying respective I or Qsignals in the respective I/Q circuits 402, 404. The respective poweramplifier circuit 450 a, 450 b is positioned into each of the respectiveIn-phase and Quadrature circuits 402, 404. The local oscillator 430 andfrequency divider circuits 432 can be similar as with the circuit ofFIG. 4 with modifications as are necessary. After mixing withinrespective mixers 418, 420, the respective I and Q signals are eachbandpass filtered within the respective bandpass filters 442 a, 442 b,and then each power amplified by respective power amplifier circuits 450a, 450 b such that the separate In-phase and Quadrature signals arepower amplified separately and not after being combined as in thecircuit of FIG. 4. Afterward, the respective I and Q signals are powercombined within a power combiner 460 and the resultant signal filteredwithin a low pass filter 462.

This I/Q modulation and power amplification circuit 400 in thisnon-limiting example uses two separate power amplifier circuits 450 a,450 b with 3 dB less output power as compared to a more conventionalsingle power amplifier circuit positioned after combining such as shownin FIG. 4, resulting in better linearity of the power amplifier circuit,while still maintaining the same output power through a 3 dB powercombiner 460 as a non-limiting example. The power combiner 460 isolatesthe output from the input such that the circuit 400 can prevent a poorantenna match from directly affecting the power amplifier and radiofrequency (RF) performance. With higher and more efficient poweramplifier circuits 450 a, 450 b as described for each I/Q circuit 402,404, it is possible to gain longer battery life. Because it is possibleto use more linear power amplifiers, there is less harmonic emissionfrom the power amplifier output.

IQ modulation is achieved with the circuit shown in FIG. 5, but alsodigital amplitude, frequency and phase modulation is achieved in anefficient manner. Better linearity and power-added efficiency occursbecause of using smaller power amplifier circuits such as associatedwith a mobile wireless communications device to achieve a desired outputpower, for example, greater than 33 dBm. This type of I/Q modulation andpower amplification circuit 400 allows a more flexible digitalmodulation for different modulation schemes with similar hardwarearchitectures. It is also possible to implement the circuit 400 on asingle transceiver chip such as shown by the line at 470 due to the useof the respective power amplifier circuits 450 a, 450 b, transmitting 3dB less of RF power than a normal single power amplifier circuit 350such as shown in FIG. 4. The IQ modulation and power amplificationcircuit 400 shown in FIG. 5 includes as a non-limiting example a 3 dBpower combiner 460 such as a quadrature hybrid power combiner andprovides an easier power amplifier match for better output power andimmunity to mobile antenna impedance change. The power combiner 460 alsoallows the cancellation of even order transmit harmonics, which in turn,will make any harmonics filter design easier with less insertion lossand associated factors.

A quadrature hybrid power combiner 460 as a non-limiting example can beformed using different techniques and typically combines two, usuallyequal amplitude, quadrature-phased input signals into a single outputsignal. The combiner could use lumped element circuits, strip linecircuits, or other circuits. The strip line circuits can be used inthose applications requiring low loss or high power or both. Typically,a fundamental circuit element is a 3 dB quarter-wave coupler and formedas a four port network. The signal applied to a first port could besplit equally between a second and third port with one of the outputshaving a relative 90-degree phase shift. When the second and third portsare terminated into matching impedances, the signal applied to the firstport is typically transmitted to a load connected to the second andthird ports such that a fourth port receives negligible power and is“isolated.” An impedance mismatch at the second port could reflect somesignal power back from the second port to be divided proportionallybetween the first and fourth ports. It is also possible to vary therelative input/output phasing even though the relationship between theoutput ports is maintained at 90 degrees. It may be possible to form alumped element construction with one or more toroidal cores. Typicallyin a lumped element design, the insertion loss is related to the Qvalues of different components used in the network. In a strip linecomponent, however, the insertion loss can result from the resistance ofconductors and a mismatch loss at input/output ports and directivityloss. Thicker conductors could reduce some of that loss.

The I/Q modulation and power amplification circuit 400 shown in FIG. 5overcomes the technical drawbacks and problems associated with the typeof circuit 300 shown in FIG. 4 in which only one power amplifier circuit350 is used after power combining, especially with power amplifierdesigns for GSM/GPRS/EDGE systems to achieve both GMSK and 8 PSK.Different RF transceiver systems have different transceiverarchitectures for digital frequency and phase modulations with IQmodulation.

The I/Q modulation and power amplification circuit 400 of FIG. 5 withrespective power amplifier circuits 450 a, 450 b in each of I and Qcircuits 402, 404 allows greater control over any power amplifier driverand/or power amplifier biasing, even when using either open loop systemsor larger or smaller closed loop systems. Controllers 480 a, 480 b (orone controller) are operative with the respective power amplifiercircuit 450 a, 450 b and controls gain and other factors. Thecontrollers 480 a, 480 b can be open loop or closed loop control (asshown by the dashed feedback line in each circuit). The I/Q modulationand power amplification circuit 400 shown in FIG. 5 unifies the IQmodulation scheme with linear/higher efficiency/higher powerrequirements of power amplifier designs such that different types ofdigital modulations, for example, AM, FM and PM can be fulfilled. Also,the two respective power amplifier circuits 450 a, 450 b shown in FIG. 5can be calibrated to achieve high linear/efficiency/power amplifierdesign with low harmonics and less sensitivity to antenna loading.

In one non-limiting aspect, the power combiner 460 is operative as a 3dB quadrature hybrid combiner as noted before. With this circuit designas described, two power amplifier circuits 450 a, 450 b could be usedwith only 30 dBm (1 watt) output power to achieve 33 dBm. The loss dueto the power combiner 460 could be about 0.2 to about 0.3 dB, whichcould handled using a sharp low pass filter 462 to force down the thirdharmonics of the power amplifier. Thus, it is possible that the poweramplifier circuits 450 a, 450 b with 30 dBm output can be established toachieve 33 dBm output. Typically, using the 3 dB quadrature hybrid powercombiner 460, it is possible to isolate the antenna matching from thepower amplifier matching to obtain better transmission radiated power(TRP). As a result, the antenna design does not require more than onefeed port to incorporate the power combiner as described.

It should be understood that the quadrature hybrid power combiner 460can be tolerable to the mismatch of an antenna load impedance. Also, thequadrature hybrid gives greater reflectivity for phase and frequencymodulation. Thus, efficient amplitude modulation can occur by changingthe bias of the power amplifier circuits 450 a, 450 b for each of theIn-phase and Quadrature circuits 402,404 and give greater flexibility incircuit function.

FIGS. 6, 7A and 7B show an improvement over the I/Q modulation and poweramplification circuit shown in FIG. 5 in which the linearity is improvedwith respect to each I and Q power amplifier shown in FIG. 5. Also, theI and Q amplitude and phase imbalance issues are improved and theefficiency issues of I and Q power amplifiers with different RF outputpower levels is enhanced. As noted before, the circuit shown in FIG. 5includes a controller 480 a, 480 b that controls the feedback loop, forexample, for the purpose of pre-distortion. The circuit shown in FIGS.6, 7A and 7B provides greater efficiency to how the controller, shown asmicroprocessor and baseband processor 530, can be configured and usesthe circuitry to effect better control, while also provides for bettercurrent sensing and a controlled power supply. When describing thesecomponents, reference numerals begin in the 500 series.

A double I/Q modulation scheme is illustrated in FIG. 6. Signals fromthe power amplifiers combine in a better and more efficient manner and adouble I_Q modulator system is used as illustrated with the use ofcomplex I and Q coefficients to form I_I, I_Q, Q_I, and Q_Q signalcomponents shown as the signal inputs. The mathematical functions areillustrated. The Q_Q signal component is inverted 180 degrees by circuit501. Each signal passes through a respective low pass filter 502 a-d andinto mixers 504 a-d. The circuits form a respective In-phase modulatorand mixer circuit and Quadrature modulator and mixer circuit and formsrespective Q_I mixer, Q_Q mixer and I_I and I_Q mixers. A sine signalgenerated from a frequency generator as a local oscillator (LO) 503 ispassed into a 90-degree frequency divider circuit 505 a, 505 b to addcosine and sine function 90-degree phase shifts for each of therespective I_I, I_Q, Q_I, and Q_Q signals as illustrated. After mixing,the respective signals pass into a respective I and Q summer 506 a, 506b and through a respective I and Q bandpass filter 510 a, 510 b into therespective I and Q power amplifiers 512 a, 512 b. The signal output fromthe power amplifiers 512 a, 512 b each passes through a respective I andQ power amplifier matching circuit 514 a, 514 b and are combined in the3 dB quadrature combiner 520. The mathematics showing that the propercombining of signals can occur is illustrated.

The double I/Q modulator circuit in FIG. 6 is shown generally at 500 inFIGS. 7A and 7B, which is part of the larger circuit forming the I and Qmodulation and power amplification circuit shown generally at 525,receives the I_Q, Q_I, and Q_Q signals as digital, baseband signals (Iand Q signals) from the microprocessor and baseband processor showngenerally at 530, which acts a controller and is also referred herein asa processor or controller. The circuit as shown in FIGS. 7A and 7Bincludes a respective I and Q switched power supply 532 a, 532 b foreach of the I and Q power amplifiers 512 a, 512 b also identified asPA_I and PA_Q. The output from the quadrature 3 dB combiner 520 isoutput into a directional coupler 536 and signals are output through alow pass filter 538 and a connector 540, which in the instantnon-limiting example is a 50-ohm connector. The signal passes from theconnector 540 into an antenna match circuit 542 and is transmitted as asignal output through the antenna 544.

Signals such as various control signals are received into the switchedpower supply 532 a, 532 b and other signals are fed back to theprocessor 530, for example, as I_I and Q_I sensor signals. The switchedpower supply circuits 532 a, 532 b receive various amplitude, sensor andother related signals from the processor 530 as illustrated.

It should be understood that each of the II, IQ, Q_I and Q_Q signalsfrom the processor 530 are generated as digital signals and pass througha respective digital-to-analog converter 550 before passing into therespective low pass filters 502 a-d. Bias signals for the I and Qsignals are generated from the processor 530 and each pass through adigital-to-analog converter (DAC) 552 a, 552 b and into respective I andQ power amplifiers 512 a, 512 b to provide bias control to theamplifiers. A power detect signal is received from the directionalcoupler 536 via resistor R and R-det and into a power detector circuit556 and passes through the analog-to-digital converter (ADC) 558 to bereceived by the processor 530. Signals from the power amplifier matchcircuit 514 a, 514 b are received into low pass filters 560 a, 560 b forrespective I and Q demodulator circuits 570 a, 570 b that each includethe appropriate mixers 572, phase shifter and frequency dividers 574 andlow pass filters 576 and analog-to-digital converters (ADC) 578 for eachof the I and Q demodulator circuits 570 a, 570 b. The signal outputsinclude an I_IF signal, I_QF signal, Q_IF signal, and Q_QF signal. Asignal from the directional coupler 536 also passes through an R_IQresistor and through a low pass filter 580 into another IQ demodulator582 as illustrated, which includes mixers 584, frequency divider 586,low pass filters 588 and ADC 590.

In operation, a very small portion (about −30 dB, or 0.1%) is taken outof the I_PA (512 a) output (the same is done at Q_PA (512 b) output andthe I signal is described as an example). The signal passes through thelow pass filter 560 a and is demodulated via the IQ demodulator, and inthis example, the I demodulator 570 a. The demodulated I and Q basebandsignals will be low pass filtered and analog-to-digitally converted inrespective circuits 576, 578. These demodulated digital I and Q signalswill be compared with the digital I and Q portions of the original Ibaseband digital output signal to the I/Q modulator 500. The amplitude,frequency and phase modulation errors will be detected. After analyzingthe error messages, proper digital adjustments will be made on the Idigital output signal in this example. Also, proper adjustment toimprove the linearity of the I_PA power amplifier 512 a can be done viaan I_am (amplitude) signal to the I_PA bias control (Bias_I). Theadjustment to further the amplitude modulation can also be done via anI_AMP signal from the processor to the I_PA power supply voltage 532 a.As to the Q side, the same can be accomplished.

In order to achieve the optimal and balanced IQ modulated PA outputsignal, the directional coupler 518 with about 20 dB coupling factor isadded at 3 dB quadrature output from the quadrature combiner 520. Thecoupled signal via resistor R will be divided into two parts. One partof the signal is matched to the input of the power detector circuit 556via the R_det resistor. The analog output of the detector 556 will beA/D converted by the ADC into 558 a digital signal and compared with theoriginal Vramp [=(I_am+Q_am)/2]. The error will be corrected bypre-distorting I_am and Q_am (amplitude) signals to compensate for theamplitude error. The other part of the signal will be matched to theinput of the low pass filter (LPF) 580 via resistor R_IQ. The low passfilter 580 will remove the harmonics of the transmitted frequencies. Thefiltered signal will be demodulated by the 3rd IQ demodulator 582. IQ_QFand IQ_QF signals as the output will represent the demodulated digital Iand Q signals. These signals will be compared with original digitalsignals I and Q by the processor 530. The amplitude, phase and frequencyerrors are detected. These errors will be corrected by pre-distortingthe digital I and Q signals before being fed into the D/A converters 550and the IQ modulators, respectively. This, of course, corresponds to thefeed forward process.

As noted before, by using I and Q PA's 512 a, 512 b to replace theconventional one PA solution, switched power supplies 532 a, 532 b areused for I and Q PA's 512 a, 512 b, respectively. The I or Q PA's 512 a,512 b will consume about half of the current to allow the system to usecommercially available switched power supplies 532 a, 532 b. The I and QPA's 512 a, 512 b will be controlled by TX_EN signal from the processor530 to turn on the amplifier. The supply voltage to both amplifiers willbe set by TX_PCL signal from the processor 530 with respect to thetransmitted power. The higher the output power (i.e., higher PCL level),the higher the supply voltage, which is also corresponding to I_am andQ_am for the amplifiers' bias setting. By adjusting both amplifiers'bias and supply voltage, the system places the amplifiers into the mostDC power efficient operating condition. I_I_sensor and Q_I_sensorsignals received from the I and Q power supplies into the processor willalso be used to monitor the currents flowing into the amplifiersrespectively, in order for better bias control of the amplifiers. I_AMPand Q_AMP signals back to the power supplies can be used for (1) analogand/or digital amplitude modulation; (2) Pre-distortion for the poweramplifier linearization; and (3) dynamically adjusting the supplyvoltage during each burst for better amplifier's dynamic range. ATX_STBY signal is used to keep the switched power suppliers in standbymode in order to be ready for next instant transmission.

Many modifications and other embodiments will come to the mind of oneskilled in the art having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it isunderstood that various modifications and embodiments are intended to beincluded within the scope of the appended claims.

1-25. (canceled)
 26. A communications device comprising: an In-phase (I)circuit configured to modulate and amplify a digital, baseband I signal;a Quadrature (Q) circuit configured to modulate and amplify a digital,baseband Q signal; a power combiner configured to receive the separatelymodulated and amplified I and Q signals and output a combined I and Qsignal; an I demodulator circuit configured to demodulate a feedbacksignal from the I circuit and produce a demodulated I signal; a Qdemodulator circuit configured to demodulate a feedback signal from theQ circuit and produce a demodulated Q signal; and a processor configuredto compare the digital, baseband I and Q signals with the demodulated Iand Q signals to compensate for at least one of an amplitude error, afrequency error, and a phase modulation error.
 27. The communicationsdevice according to claim 26, wherein the processor is configured topredistort the digital baseband I and Q signals fed to the I and Qcircuits.
 28. The communications device according to claim 26, whereinthe I circuit comprises an I modulator and mixer circuit and an I poweramplifier circuit coupled thereto; and wherein the Q circuit comprises aQ modulator and mixer circuit and a Q power amplifier circuit coupledthereto
 29. The communications device according to claim 28, wherein theI modulator and mixer circuit receives I_I and I_Q input signals toproduce an I signal to the I power amplifier; and wherein the Qmodulator and mixer circuit receives Q_I and Q_Q input signals toproduce a Q signal to the Q power amplifier.
 30. The communicationsdevice according to claim 29, wherein the I modulator and mixer circuitcomprises an I_I mixer and I_Q mixer configured to receive respectiveI_I and I_Q signals and a frequency divider circuit associated therewithconfigured to impart a ninety degree phase shift, and an I summerconfigured to receive signals from the mixers and produce an I signal.31. The communications device according to claim 29, wherein the Qmodulator and mixer circuit comprises a Q_I mixer and Q_Q mixerconfigured to receive respective Q_I and Q_Q signals and a frequencydivider circuit associated therewith configured to impart a ninetydegree phase shift, and a Q summer configured to receive signals fromthe mixers and produce a Q signal.
 32. The communications deviceaccording to claim 28, wherein the processor is configured to outputcontrol signals for controlling each of the power amplifier circuits,and control respective biasing in each power amplifier circuit.
 33. Thecommunications device according to claim 28, wherein each of the I and Qdemodulator circuits comprise mixers and a frequency divider associatedtherewith configured to impart a ninety degree phase shift.
 34. Thecommunications device according to claim 26, further comprising an I/Qdemodulator circuit connected to the processor and configured to receivea signal from the output of the power combiner.
 35. The communicationsdevice according to claim 26, further comprising a power detectorconnected to the processor and configured to receive a signal from theoutput of the power combiner and output a signal that is compared withan original power.
 36. The communications device according to claim 26,wherein the power combiner comprises about a 3 dB power combiner. 37.The communications device according to claim 26, wherein the powercombiner comprises a quadrature hybrid power combiner.
 38. A mobilewireless communications device comprising: a housing; an antenna carriedby the housing; at least one circuit board carried by the housing andincluding radio frequency (RF) circuitry carried by the at least onecircuit board and comprising an In-phase (I) circuit configured tomodulate and amplify a digital, baseband I signal, a Quadrature (Q)circuit configured to modulate and amplify a digital, baseband Q signal,a power combiner configured to receive the separately modulated andamplified I and Q signals and output a combined I and Q signal, an Idemodulator circuit configured to demodulate a feedback signal from theI circuit and produce a demodulated I signal, a Q demodulator circuitconfigured to demodulate a feedback signal from the Q circuit andproduce a demodulated Q signal, and a processor configured to comparethe digital, baseband I and Q signals with the demodulated I and Qsignals to compensate for at least one of an amplitude error, afrequency error, and a phase modulation error.
 39. The mobile wirelesscommunications device according to claim 38, wherein the processorpredistorts the digital baseband I and Q signals fed to the I and Qcircuits.
 40. The mobile wireless communications device according toclaim 38, wherein the I circuit comprises an I modulator and mixercircuit and an I power amplifier circuit coupled thereto; and whereinthe Q circuit comprises a Q modulator and mixer circuit and a Q poweramplifier circuit coupled thereto
 41. The mobile wireless communicationsdevice according to claim 40, wherein the I modulator and mixer circuitis configured to receive I_I and I_Q input signals to produce an Isignal to the I power amplifier; and wherein the Q modulator and mixercircuit is configured to receive Q_I and Q_Q input signals to produce aQ signal to the Q power amplifier.
 42. The mobile wirelesscommunications device according to claim 41, wherein the I modulator andmixer circuit comprises an I_I mixer and I_Q mixer configured to receiverespective I_I and I_Q signals and a frequency divider circuitassociated therewith configured to impart a ninety degree phase shift,and an I summer configured to receive signals from the mixers andproduce an I signal.
 43. The mobile wireless communications deviceaccording to claim 41, wherein the Q modulator and mixer circuitcomprises a Q_I mixer and Q_Q mixer configured to receive respective Q_Iand Q_Q signals and a frequency divider circuit associated therewithconfigured to impart a ninety degree phase shift, and a Q summerconfigured to receive signals from the mixers and producing a Q signal.44. The mobile wireless communications device according to claim 40,wherein the processor is configured to output control signals forcontrolling each of the power amplifier circuits, and control respectivebiasing in each power amplifier circuit.
 45. The mobile wirelesscommunications device according to claim 40, wherein each of the I and Qdemodulator circuits comprise mixers and a frequency divider associatedtherewith configured to impart a ninety degree phase shift.
 46. Themobile wireless communications device according to claim 38, furthercomprising an I/Q demodulator circuit connected to the processor andconfigured to receive a signal from the output of the power combiner.47. The mobile wireless communications device according to claim 38,further comprising a power detector connected to the processor andconfigured to receive a signal from the output of the power combiner andoutput a signal that is compared with an original power.
 48. The mobilewireless communications device according to claim 38, wherein the powercombiner comprises about a 3 dB power combiner.
 49. The mobile wirelesscommunications device according to claim 38, wherein the power combinercomprises a quadrature hybrid power combiner.
 50. The mobile wirelesscommunications device according to claim 38, wherein the RF circuitry isconfigured to generate Global Systems for Mobile (GSM) packet bursts.51. A method of operating a communications device comprising: modulatingand amplifying a digital, baseband In-phase (I) signal using an Icircuit; modulating and amplifying a digital, baseband Quadrature (Q)signal using a Q circuit outputting a combined I and Q signal using apower combiner receiving the separately modulated and amplified I and Qsignals; demodulating a feedback signal from the I circuit using an Idemodulator to produce a demodulated I signal; demodulating a feedbacksignal from the Q circuit using a Q demodulator to produce a demodulatedQ signal; and comparing the digital, baseband I and Q signals with thedemodulated I and Q signals using a processor to compensate for at leastone of an amplitude error, a frequency error, and a phase modulationerror.
 52. The method according to claim 51, further comprising usingthe processor to predistort the digital baseband I and Q signals fed tothe I and Q circuits.